Suziequeue - are you in the UK ?
A quick phonecall to your environmental health department will get it all cleared up (as it's them who'll have to inspect you and approve your premises etc)
I'd be wary of doing any kind of on-line course (or any course for that matter) without checking first if it's a recognised qualification
My dad is a cook in a local care home (with all his food hygiene quals.) a new cook started with certificates for this, that and another - it was only when the 'official' from environmental health turned up they discovered her qualifications weren't worth the paper they were written on
You'll also need product liability insurance & need to comply with weights & measures and labelling regulation....but your environmental health officer/advisor will be able to keep you right on all that.
HTH
Karen